@article{MZM_1971_9_5_a3,
     author = {Yu. N. Subbotin},
     title = {A~relation between spline approximation and the problem of the approximation of one class by another},
     journal = {Matemati\v{c}eskie zametki},
     pages = {501--510},
     publisher = {mathdoc},
     volume = {9},
     number = {5},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1971_9_5_a3/}
}